There are white criminals.
There are black criminals.
For the foreseeable future, there will always be criminals, and there will always be crime. Criminals do violent things sometimes, because they are criminals. They are expected to do harmful, destructive, and sometimes deadly anti-social things. That's what criminals do.
Most criminals aren't organized into tidy hierarchical groups. They don't show up for work and have a staff meeting. They aren't accountable for their actions, and they don't get structured training.
You can't call a meeting for all criminals. "Hey criminals, we're going to have a meeting and discuss procedure. Maybe we could find ways for you to shoot people less often."
Police officers, on the other hand, are not supposed to do harmful, destructive, sometimes deadly things. But some police officers do. Police officers, however, are organized into hierarchical groups. They show up for work and write their names down on rosters. They receive structured training.
Police officers can be called into meetings. They can receive better training. They can be told, "Hey, we're going to have a meeting and discuss procedure. Maybe we could find ways for you to shoot people less often."
If a white civilian kills another white civilian, and a week later, a cop kills a white civilian, no one says, "Well, there is white-on-white crime, therefore, it is okay for cops to kill white people."
The logic just isn't there. It isn't even an argument. Those pointing out black-on-black crime as some sort of defense or rationalization of cop-on-black crime should ask themselves why they are defending not fixing something that could be fixed.